In general, a roll screen is used in home, an office, a restaurant or the like in place of a curtain. A screen is made from fabrics or synthetic resins. By pulling a ball chain coupled to a sprocket mounted to a bracket, the screen is released from a winding pipe and moves down by an elastic force of a spring. Then, the screen is stopped at a certain position for blocking sunlight through a window.
As shown in FIG. 1, a prior art roll screen 10 comprises two brackets 9 fixed to a window frame or a wall, and rotating means 5 and speed-reducing means 8 mounted to the brackets 9. A winding pipe, around which a screen is wound, is provided while surrounding the rotating means 5 and the speed-reducing means 8.
The rotating means 5 includes a rotating body 1, a connecting shaft 3 mounted to the rotating body 1, and a rotating piece 2 coupled to an end portion of the connecting shaft 3. A spring 4 is provided around the connecting shaft 3. One end of the spring 4 is supported by the rotating body 1, and the other end of the spring 4 is supported by the rotating piece 2. The rotating piece 2 moves left and right along the connecting shaft 3 by the elastic force of the spring 4.
The speed-reducing means 8 includes a rotating body 1 having an adjuster, a speed reducer 6 connected to the rotating body 1, a screw shaft 7 connected to the speed reducer 6, and a speed-reducing nut 7a coupled to the screw shaft 7.
By pulling a ball chain 1a coupled to a sprocket (not shown) mounted to the rotating body 1, the screen is rolled up to the uppermost position or adjusted to stop at a position to be desired. However, to adjust the height of the screen is troublesome because a user should pull the ball chain continuously.
To solve the above problem, an electromotive roll screen has been developed. However, since the prior art electromotive roll screen has a complicated structure, the installation, manipulation and maintenance thereof are difficult. Further, the prior art electromotive roll screen consists of relatively many components including electrical elements, which causes an increase of manufacturing costs.